mgs
[Top] [All Lists]

Re: [Mgs] MGB valve cover/crankcase venting

To: Rick Lindsay <rolindsay@yahoo.com>, Paul Hunt
Subject: Re: [Mgs] MGB valve cover/crankcase venting
From: Barney Gaylord <barneymg@mgaguru.com>
Date: Sun, 13 Jan 2008 11:17:13 -0600
At 06:13 AM 1/13/2008 -0800, Rick Lindsay wrote:
>.... for MY car, not Danny's. ....
>
>.... The engine, I believe, is a '65 18GB. ....
>....
>.... What I called a "gulp valve" is really the "crankcase emission 
>valve".  The bottom of the valve is plumbed to the inlet 
>manifold.  The side port of the valve connects to the hose from the 
>forward lifter gallery cover.

I have ony good things to say about the PCV valve.  I wish I had one 
on my MGA, but alas I am either too cheap or too lazy to make the 
modification.  It is a neat gadget that does nice things and is 
generally quite reliable.

The functional description is "vacuum regulated flow control 
valve".  It connects the crankcase to the inlet manifold to 
positively ventilate the crankcase to keep it clean inside and burn 
emissions fumes.  In the process it generates and regulates a small 
vacuum in the crankcase that greatly reduces oil leakage and may 
totally eliminate dribbles under your car.

>....
>    So the question becomes, if I effective plug the line from the 
> cover to the valve, will the crankcase 'breathe' adequately at the 
> stock filler cap?
>....

No.  If you block off the inlet port to the PCV valve it stops all 
air flow there, same as removing the valve and plugging ports in the 
inlet manifold and front tappet cover.  That would defeat crankcase 
ventillation, allowing buildup of water vapor and certain acids and 
soot in the crankcase, resulting in rapid accumulation of sludge in 
the oil and crud all over the inside of the engine.  One indication 
of inadequate crankcase ventillation is accumulation of condensed 
water and oil emulsion in the valve cover, looking like dirty 
mayonase.  Blocked valve cover port also builds a slight pressure in 
the crankcase forcing crankcase blow-by gasses to escape via the 
valve cover vent.  That can leave oily deposits on the valve cover at 
the same time the engine is dribbling oil on the floor.

If it was mine, I'd keep the PCV valve functional.  If the rubber 
diaphragm should leak for any reason, the valve remains closed 
similar to being plugged, or having the ports plugged (see prior 
paragraph).  It is a very simple task to R&R the wire clip on top of 
the valve for cleaning or replacement of the rubber diaphragm.  If 
the valve should ever get stuck open you get excess vacuum in the 
crankcase, resulting in excess oil consumption and possible bad idle 
condition.  Even then it is an easy task to disassemble the valve for 
cleaning.  When the PCV valve is working properly, they very seldom fail.
_______________________________________________
Support Team.Net  http://www.team.net/donate.html




Mgs@autox.team.net
http://autox.team.net/mailman/listinfo/mgs

http://www.team.net/archive

<Prev in Thread] Current Thread [Next in Thread>